14.1.2 When tests fail

When the tests in the old test suite are run via make check,
output is caught in per-test tests/test-name.log files
and summarized in the test-suite.log file. The exit status of each
program tells the Makefile whether or not the test succeeded.

If a test fails, it means that there is either a programming error in
libtool, or in the test program itself.

To investigate a particular test, you may run it directly, as you would
a normal program. When the test is invoked in this way, it produces
output that may be useful in determining what the problem is.